Input vector set for position detection of PM motors

ABSTRACT

A method of determining angular position (θ) of a rotor of an N-phase permanent magnet motor (PMM). A processor having an associated stored angular position determination (APD) algorithm is programmed to implement the algorithm to cause an associated motor controller to execute steps including forcing one vector at a time a phase vector set of current or voltage vectors to stator terminals of windings for the N-phases a positive and negative magnitude vector, wherein the vector magnitude is sufficiently small to not move the rotor, and a time duration for the forcing current or voltage vectors is essentially constant. The resulting stator current or voltage levels are measured for each current or voltage vector. An N-dimension current vector or voltage vector is generated from superposition of the resulting stator current levels or resulting stator voltage levels. The N-dimension current vector or voltage vector is used to determine angular position.

CROSS REFERENCE TO RELATED APPLICATIONS

This continuation application claims priority to U.S. patent applicationSer. No. 16/740,517, filed Jan. 13, 2020, which claims priority to U.S.patent application Ser. No. 16/288,327, filed Feb. 28, 2019 (now U.S.Pat. No. 10,574,165), which application claims priority to U.S. patentapplication Ser. No. 15/916,945, filed Mar. 9, 2018 (now U.S. Pat. No.10,263,555), which application claims priority to U.S. patentapplication Ser. No. 15,250,306, filed Aug. 29, 2016 (now U.S. Pat. No.9,917,542), which application claims priority to U.S. patent applicationSer. No. 14/721,786, filed May 26, 2015 (now U.S. Pat. No. 9,431,947),which application claims priority to and the benefit of ProvisionalApplication Ser. No. 62/054,498, filed Sep. 24, 2014, all of which areherein incorporated by reference in their entirety.

FIELD

Disclosed embodiments relate to permanent magnet motors (PMNs), and morespecifically to determining the angular position of PMMs for use by amotor controller for position, velocity or current/torque control of thePMM.

BACKGROUND

An electric motor is a machine that converts electrical energy intomechanical energy. Electric motors include DC motors and AC motors. Onetype of AC motor is an AC induction motor. An AC induction motor istypically driven by 3-phase alternating current provided by an electricmotor controller coupled to a 3-phase inverter. The AC motor includes anoutside stationary stator having coils supplied with alternating currentto produce a rotating magnetic field, which induces a current in therotor windings. As the current flows through the rotor windings, asecond magnetic field is generated which interacts with the magneticfield from the stator to produce motion. The rotor is attached to theoutput shaft that is given a torque by the rotating magnetic field. Theinteraction of the rotor field and the stator field causes rotation ofthe rotor which can be used to perform work.

Another type of AC motor is a PMM. PMMs have permanent magnets locatedon the rotor and copper windings located on the stator. The alternatingcurrent in the stator windings produces a rotating magnetic field whichinteracts with the magnetic field from the rotor magnets to producemotion. The frequency at which the stator current oscillates determinesthe rotor's angular velocity and the resulting angular position.

SUMMARY

This Summary is provided to introduce a brief selection of disclosedconcepts in a simplified form that are further described below in theDetailed Description including the drawings provided. This Summary isnot intended to limit the claimed subject matter's scope.

Disclosed embodiments include permanent magnet motors (PMM) motorcontrollers implementing current or voltage sensed control forcontrolling N-phase PMMs that include a disclosed motor control systemand a related rotor angular position determination (APD) algorithm andvelocity estimation algorithm. The APD system includes a controller (APDcontroller) block that determines the state of the position detectionsystem and the resulting input signal for the position detectionalgorithm, a signal generator (SIG GEN) block that provides signals usedfor generating a voltage or current input vector set coupled to thestator terminals of the PMM, and an estimation (EST) block thatimplements the APD algorithm and velocity estimation algorithm.

The control scheme utilized with disclosed APD algorithms can be fieldoriented control (FOC). However, disclosed APD algorithms areindependent of the control system as they can be operate in phasecoordinates which removes the need for FOC. Other control schemes whichcan be used include the motor controller operating in the α/β frame,where the voltage/current in each coordinate is independently controlledwhich is then transformed via a space vector (SV) generator to the A/B/Cframe. The motor controller can also operate in the A/B/C frame to allowcontrol of the voltage/current of each motor phase directly.

Disclosed angular position determination systems and related methodsdetermine the initial angular position at zero speed or near zero speed.A processor has an associated memory storing an APD system including anAPD controller algorithm which implements an APD controller block, a SIGGEN algorithm which implements a SIG GEN block, and an estimatoralgorithm which implements an EST block. The processor is programmed toimplement the APD controller algorithm to execute steps that cause a SIGGEN algorithm to force a phase vector set comprising voltage or currentvectors one vector at a time to stator terminals of the stator windings,measure resulting stator current or voltage levels, implement an APDalgorithm that generates an N-dimension current vector or voltage vectorfrom the measured current or voltage levels, and uses the N-dimensioncurrent vector or voltage vector to determine the angular position.

The phase vector set includes a positive magnitude vector and a negativemagnitude vector for applying to each of the N stator windings. Amagnitude of the current vectors or voltage vectors used are allsufficiently small to not move the rotor, and a time duration for theforcing the respective vectors is essentially fixed for a given motor.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, wherein:

FIG. 1A is a plot of magnetic flux density B, and how it typicallyvaries as a function of magnetic field strength, H, for typical PMMstator core material such as iron. FIG. 1B is a B-H curve showingoperating point vs. angular position of the rotor. FIG. 1C is a plot ofthe magnetic flux, ψ, as a function of current, I, for a typical PMMstator core.

FIG. 2A is a block diagram of a motor control system with a motorcontroller for implementing current sensed control for controlling athree-phase PMM having a disclosed angular position determination systemimplementing current sensed control including an APD controller blockthat determines the state of the angular position determination systemand specifies the desired signals needed by the SIG GEN block and theAPD algorithm, a SIG GEN block that provides signals used for generatinga voltage input vector set coupled to the stator terminals, and an ESTblock, according to an example embodiment.

FIG. 2B is a block diagram of a motor control system with a motorcontroller for implementing voltage sensed control for controlling athree-phase PMM having a disclosed angular position determination systemincluding an APD controller block that determines the state of theangular position determination system and specifies the desired signalsneeded by the SIG GEN block and the APD algorithm, a SIG GEN block thatprovides signals used for generating a current input vector set coupledto the stator terminals and an EST block, according to an exampleembodiment.

FIG. 3 is a block diagram of an example microcontroller unit (MCU) chipimplementing the motor controller shown in FIG. 2A or FIG. 2B, accordingto an example embodiment.

FIG. 4 is a flow chart that shows steps for an example method fordetermining the angular position of a rotor of a PMM using an inputphase vector set, according to an example embodiment.

FIG. 5 show experimental results from applying a disclosed APD algorithmto a surface mounted PMM, showing the calculated angular position of therotor vs. actual angular position of the rotor at 10 degree increments.

DETAILED DESCRIPTION

Example embodiments are described with reference to the drawings,wherein like reference numerals are used to designate similar orequivalent elements. Illustrated ordering of acts or events should notbe considered as limiting, as some acts or events may occur in differentorder and/or concurrently with other acts or events. Furthermore, someillustrated acts or events may not be required to implement amethodology in accordance with this disclosure.

Also, the terms “coupled to” or “couples with” (and the like) as usedherein without further qualification are intended to describe either anindirect or direct electrical connection. Thus, if a first device“couples” to a second device, that connection can be through a directelectrical connection where there are only parasitics in the pathway, orthrough an indirect electrical connection via intervening itemsincluding other devices and connections. For indirect coupling, theintervening item generally does not modify the information of a signalbut may adjust its current level, voltage level, and/or power level.

Before the disclosed angular position algorithm is developed below, thedependence of the motor reluctance on the angular position of the motorrotor is explained. The magnetic model of a surface mounted PMM assumesthat the stator resistance and inductance values are constant, which istrue as long as the magnetic system (motor windings, motor stator poles,motor rotor permanent magnets) is operating along the linear region ofthe B/H curve as shown in the typical B/H curve for an iron stator coreof a PMM. FIG. 1A plots magnetic flux density, B, with units of tesla,(1 tesla=1 Wb/m²) as a function of magnetic field strength, H, withunits of A/m for a given rotor angular position that shows how Btypically varies with H. It is noted that B is proportional to voltage(Wb=V·sec/rad) and H is proportional to the stator winding current.

It can be noticed in FIG. 1A that there is a linear region between zeroand Bmag, a nonlinear region and a saturation region for both positiveand negative B field strengths. The operating point on the B/H curve isdetermined by the flux generated by the permanent magnets mounted to thePMM's rotor, as shown by the point (H_(mag), B_(mag)) in FIG. 1A. Theexact location of the operating point depends on the field strength ofthe permanent magnet, the field strength of the iron core generated bythe current flowing through the stator windings and the orientation ofthe permanent magnets with respect to the stator windings.

FIG. 1B is a B-H curve showing the operating point vs. rotor orientation(angular position). The magnetic operating point of the PMM's statorcore as a function of rotor angular position with respect to a statorwinding for several orientations around one electrical cycle (2π). Thedistance between the points on the curve depends upon the orientation ofthe rotor with respect to the energized stator winding, the currentlevel in the stator winding and the magnetic permeability of the statorcore material. Notice that a zero value of flux density corresponds tothe case when the magnet orientation on the rotor is orthogonal to thestator winding (see Config. 3 and Config. 7).

By integrating B over the cross section of the stator core andintegrating H along the enclosed flux path, the B/H curve can betranslated into a Ψ/I (e.g., magnetic flux versus stator current) curveas shown in FIG. 1C which shows a typical ψ-I curve for a PMM statorcore. For PMMs, the operating point on the Ψ/I curve is determined bythe magnetic flux generated by these magnets, as shown by the point(I_(mag),Ψ_(mag)) in FIG. 1C as well as the orientation of the rotorwith respect to the stator windings. Just as with the B/H curve, theoperating points of the Ψ/I curve vary as a function of the rotororientation.

The slope of the Ψ/I curve at any point is the inductance (L) of thestator core, since:Ψ=L·iAs a result, for a given inductance level and ψ level in the statorcore, it is recognized that the level of the stator current (i) can bedetermined.

When a voltage is applied to a stator terminal coupled to statorwinding(s) of a particular PMM phase, the operating point on the B/Hcurve (and thus the Ψ/I curve) moves and the current level in the statorwinding(s) of each phase changes. The duration of the voltage appliedwill determine the actual stator current (i) level. To see how thisbehavior can be modelled mathematically, consider the followingdefinition for ψ:Ψ=

·

which is a vector surface integral of the magnetic flux density (B) thatis perpendicular to the surface of interest (which in this case is thecross sectional area of the PMM stator pole). The definitions and unitsof the variables found in the equation above are as follows:Ψ is the magnetic flux, in Wb

is a vector representing the magnetic flux density, Wb/m²

is vector that is normal to the surface, in units of m²

Since a Weber (e.g. Wb) is equal to a (V·sec)/rad, it is recognized onecan simply apply a voltage to the PMM stator windings for the requiredamount of time needed to generate a stator current for reaching thedesired ψ value. This concept can be expressed mathematically as:

${\Psi\left( t_{2} \right)} = {{\Psi\left( t_{1} \right)} + {\int\limits_{t_{1}}^{t_{2}}{V \cdot {dt}}}}$As the Ψ changes in value, the current (i) changes according to thefollowing relationship

$i = \frac{\Psi}{L}$As a result, the current level (i) in a given phase (stator winding)becomes a function of rotor angular position (orientation) since theflux changes with angular position.

From a magnetic circuit perspective, the flux, Ψ, in the motor isrelated to the magnetomotive force, F, of the magnetic circuit and thereluctance, R, of the motor by the following relationship:

$\Psi = \frac{F}{R}$Since the applied voltage, V, is constant, the resulting magnetomotiveforce, F, will also change over time because the current level in thewinding will increase as the voltage is applied. Using the reluctancerelationship above, a reluctance value for a given angle orientation canbe computed. For each new angle position, the flux and magnetomotiveforce values will converge to a new operating point (i.e. flux vs.magnetomotive point) due to the different flux bias caused by therotor's magnets. As a result, the motor reluctance can be used todevelop an angular position detection algorithm.

An example angular position determination system is now derived usingvoltage vector inputs to the stator terminals of a 3-phase PMM andresulting stator current outputs. As noted above, current mode controlmay alternatively be used. In the current mode control embodiment, acurrent input vector sequence is used as the input vector set, againchosen to satisfy the system constraint that the rotor does not moveduring initial position detection.

Since many different voltage input sequences can be used, a set of inputvoltage vectors is chosen that satisfies the system constraint that therotor does not move during initial position detection. An example inputvoltage sequence chosen for a 3-phase PMM can contain two sets oforthogonal phase vectors, one set is the fundamental positive magnitudephase vector set and one is the fundamental negative magnitude phasevector set, which for 3 phases shown as a, b and c can be written as:

${{Positive}{Mag}{Vector}{Set}:}{\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix} = {{\begin{bmatrix}v_{a} \\0 \\0\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = {{\begin{bmatrix}0 \\v_{b} \\0\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = \begin{bmatrix}0 \\0 \\v_{c}\end{bmatrix}}}}{{Negative}{Mag}{Vector}{Set}:}{\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix} = {{\begin{bmatrix}{- v_{a}} \\0 \\0\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = {{\begin{bmatrix}0 \\{- v_{b}} \\0\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = \begin{bmatrix}0 \\0 \\{- v_{c}}\end{bmatrix}}}}$Note that other orthogonal phase vectors sets can be used but the aboveset is a fundamental vector set because only one phase of the motor inenergized at a time, which simplifies the APD algorithm. However, theabove phase vectors sets are only example voltage vector sets anddifferent input voltage vector sets (or input current voltage sets) canbe applied without changing the fundamental operation of the algorithmprovided the system constraint that the rotor does not move duringangular position detection is satisfied.

In the case of voltage forcing, by forcing the voltage vector in eachinput vector set for essentially the same time duration, the resultingstator current levels in each phase can be measured and recorded. Oncethe current values for all six applied phase vectors have been recorded(e.g., saved to memory), superposition can be used by the APD algorithmto construct a current vector that represents the effective currentlevel in the stator winding(s) of each phase of the PMM so that therotor's angular position can be determined.

Once the resulting N-dimension current vector has been determined, asnoted above the angular position of the rotor can be found for exampleby an angular position determination equation for a 3 phase PMM based onN-phase measurements (x₁, . . . , x_(N)), where ia(t), ib(t), and ic(t)are the N-phase current vector elements in the APD equation shown below:

$\theta = {\tan^{- 1}\left( \frac{\frac{\sqrt{3}}{2} \cdot \left( {{i_{c}(t)} - {i_{b}(t)}} \right)}{{i_{a}(t)} - {\frac{1}{2} \cdot \left( {{i_{b}(t)} + {i_{c}(t)}} \right)}} \right)}$for using the APD equation above, there are several methods to obtainthe needed ia, ib and ic (or va, vb, and vc for current forcing). Forvoltage forcing, one can use different phase input vector sets, performmathematics to determine ia, ib and ic, then use the APD equation. Thereare a large number of possible linear combinations of the fundamentalpositive and negative vector sets that can be used besides thefundamental vector sets described above. For example, the followingpositive and negative vector sets can also be used.

${{Positive}{Mag}{Vector}{Set}:}{\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix} = {{\begin{bmatrix}0 \\{- v_{b}} \\v_{c}\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = \begin{bmatrix}V_{a} \\{{- 0.5} \cdot v_{b}} \\{{- 0.5} \cdot v_{c}}\end{bmatrix}}}{{Negative}{Mag}{Vector}{Set}:}{\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix} = {{\begin{bmatrix}0 \\v_{b} \\{- v_{c}}\end{bmatrix}\begin{bmatrix}V_{a} \\V_{b} \\V_{c}\end{bmatrix}} = \begin{bmatrix}{- v_{a}} \\{0.5 \cdot v_{b}} \\{0.5 \cdot v_{c}}\end{bmatrix}}}$

Also, one can repeat a given phase input vector set a plurality oftimes, average the resulting current (or voltage) sample values, andthen use the average values in the APD equation. One can also averagethe positive and negative sequences together and then use the averagevalues in the APD equation. Design parameters for disclosed APDalgorithms thus comprise what type of voltage (or current) signal touse, the time duration of the voltage (or current) signals and themethod for determining angular position of the rotor from the N-phasemeasurements (x₁, . . . , x_(N)) in the N-dimension current (or voltage)vector.

A significant benefit of using the disclosed six fundamental phasevectors (or more generally 2 vectors per phase) is that the currentlevel in each phase winding can be easily controlled. By energizing onlyone phase at a time, better control of the magnetic interaction betweenthe magnetic field generated by the stator windings and the magneticfield from the rotor magnets can be achieved. As a result, there is lessrisk of rotating the rotor.

Disclosed embodiments include angular position determination systems andPMM motor controllers therefrom including an angular positiondetermination system comprising an APD controller algorithm, a SIG GENalgorithm, an EST algorithm for determining the initial angular positionand velocity of the rotor of PMMs at zero speed or near zero speed. Itis recognized that there are two primary magnet configurations for PMMs,being surface mount magnet and interior mounted magnet types. For PMMswith surface mounted magnets, the inductance does not vary as a functionof angular position during normal operating conditions. As a result,initial angular position detection based on inductance variations canonly be used with interior mounted PMMs.

However, as shown previously, the reluctance of both of these PMM typesdoes vary as a function of angular position of the rotor during normaloperating conditions. As a result, it is recognized that this property(the reluctance of PMMs varying as a function of angular position of therotor) can be used to design an initial or low speed angular positiondetection algorithm for both types of PMMs. A disclosed angular positiondetection system uses the magnetic properties of the PMM and employs anAPD controller algorithm which determines the state of the APD algorithmand specifies the desired signals needed by the APD algorithm, and a SIGGEN algorithm enabling a phase voltage or current input vector set to beapplied to the terminals of the stator windings to allow the measurementof current or voltage levels to provide an N-dimension current vector orvoltage vector used by the APD algorithm to determine the initialangular position of the rotor at zero speed or near zero speed.

FOC is also called vector control which is known to be a variablefrequency drive (VFD) control method that applies generally to allelectric motors where there is a desire to control the magnetic flux ofthe motor in one direction and the torque produced the motor in a seconddirection, which is orthogonal to the first direction. FOC can controlthe output of three-phase motors by using two controllable VFD inverteroutput variables or can control the output of brushless DC motors.However, as described above, disclosed APD algorithms are independent ofthe control system as they can be operate in phase coordinates whichremoves the need for FOC. Other control schemes which can be used withdisclosed embodiments include the motor controller operating in thealpha/beta (α,β) frame.

FIG. 2A shows an example block diagram of a controlled motor system 200including a motor controller (controller) 220 for implementing currentsensed control for controlling a PMM 210 shown as a three-phase motorhaving a disclosed angular position determination system which includesthe APD controller block (APD controller) 240, according to an exampleembodiment. APD controller 240 determines the state of the angularposition determination system and specifies the state to the signalgenerator (SIG GEN) block 202 and to the estimator (EST) block. The SIGGEN block 202 provides signals used for generating a voltage input phasevector set coupled to the stator terminals and the EST block 215 thatruns the APD algorithm. Controller 220 includes a non-volatile (NV)memory 272, such as read only memory (ROM) or static random accessmemory (SRAM), and a processor shown as a central processing unit (CPU)275 that implements in software all the blocks in the unshaded(non-dotted) blocks shown in FIG. 2A. Hardware components of system 200such as CPU 275 and NV memory 272 are shown in dotted blocks todistinguish them from components of system 200 implemented in software.

The output of SIG GEN block 202 is added with the Tabc output of the SVgenerator 254 which is used as the input of the PWM driver 255. The SIGGEN block 202 receives a desired phase voltage signal from the APDcontroller 240. The signals provided by SIG GEN block 202 controls theamplitude and duration of the input waveforms (here voltage waveforms)applied by the 3-phase inverter 232 to the respective stator windings ofeach phase of the PMM 210 to enable measuring resulting stator currentlevels, generating an N-dimension current vector or voltage vector fromthe measured current or voltage levels, and the EST block 215 to use theN-dimension current vector to determine angular position determination.SIG GEN block 202 is synchronized with the EST block 215 by the APDcontroller 240 telling the EST block 215 which state it is in.

System 200 also includes analog circuitry 230 between the controller 220and the PMM 210 comprising power driver 231, 3-phase inverter 232, andcurrent measurement circuits 233 b. The controller 220 includesanalog-to-digital converters (ADC's) 243 b coupled to receive outputsfrom the current measurement circuits 233 b shown as “current circuits”,and a PWM driver 255 for driving the power driver 231.

The controller 220 can be a sensorless controller or can be a controllerhaving a voltage or current sensor. Controllers having sensors caninclude encoders and sensors that measure position directly and thendetermine the angular speed therefrom. Controller 220 can be implementedby a MCU, such as the MCU chip 300 shown in FIG. 3 described below.Circuitry other than a MCU can also be used to realize controller 220implementing a disclosed APD controller block 240, a disclosed EST block215 and SIG GEN block 202 algorithm, such as coprocessors oraccelerators built using application-specific integrated circuit (ASIC)logic gates or FPGAs.

The ADC's 243 b output phase currents are also coupled to the input ofthe EST block 215. The EST block 215 generates for each phase current anangular position estimate {circumflex over (θ)} and angular velocityestimate {circumflex over ({dot over (θ)})}. The {circumflex over (θ)}with a dot (.) above denote estimate angular velocity which is providedby θ EST block 215 to the speed controller 257 shown.

The ADC's 243 b output phase currents shown as Iabc is coupled to aninput of the Clarke block 241 b which performs the known Clarketransformation which takes the measured current Iabc and transforms itinto the α/β coordinate system to generate Iαβ from Iabc, which iscoupled to an input of the Park block 246 b. Park block 246 b performsthe known Park transformation to provide outputs Idq being measuredphase current values from the stator terminals of the PMM 210 which areadded to the input of the ID current controller 252 and to the input ofthe IQ current controller 251 as shown in FIG. 2A. The estimated angularposition is shown coupled to an inverse Park (iPARK) block 253 whichreceives the Vq output from IQ controller 251 and the Vd output from theID controller 252 as other inputs.

The angle position determined from the EST block 215 is coupled to theiPARK block 253, which outputs Vαβ which is coupled to SV generatorblock 254, where the output of SV generator block 254 is coupled to PWMdriver 255. The SV generator 254 computes the PWM time durations (Tabc)for each phase of the PMM 210 to produce the desired Vαβ voltage values.The output of the PWM driver 255 is coupled to an input of a powerdriver 231 that has an output coupled to drive an input of the 3-phaseinverter 232. In this embodiment current mode control embodiment the3-phase inverter 232 forces voltage onto the stator terminals associatedwith each of the three phases of PMM 210.

FIG. 2B shows an example block diagram of a controlled motor system 250including a motor controller (controller) 220′ implementing voltagesensed control having a disclosed angular position determination systemincluding a SIG GEN block 202 that provides signals used for generatinga current input vector set coupled to the stator terminals and an ESTblock 215′, according to an example embodiment. Controlled motor system250 resembles controlled motor system 200 shown in FIG. 2A except ESTblock 215′ receives a Vabc input instead of an Iabc input (as for ESTblock 215 in FIG. 2A) that is generated by the voltage measurementcircuits (voltage circuits) 233 a coupled to an output of the 3-phaseinverter 232. The output from voltage circuits 233 a is coupled to ADC243 a which generates Vabc that is coupled to an input of the EST block215′. In this voltage mode control embodiment the 3-phase inverter 232forces current on each of the phases of the PMM 210.

FIG. 3 is a block diagram depiction of an example MCU chip 300 formed inand on a substrate 305 implementing the controller 220 shown in FIG. 2Aor controller 220′ shown in FIG. 2B, according to an example embodiment.Although not shown, the MCU chip 300 generally includes other integratedcircuit modules, for example, a Universal Serial Bus (USB) controllerand a transceiver. MCU chip 300 is shown including NV memory 272,volatile data memory 273, digital I/O (interface) 274, CPU 275, andclock (or timer) 276. Core for implementing the APD algorithm includesan EST block 215 or 215′ shown as block 215″ and a core for implementingSIG GEN block 202 is shown as 202″ both stored in NV memory 272. MCUchip 300 is also shown including a digital data bus 278 and an addressbus 279.

MCU chip 300 is shown as a monolithic integrated circuit (IC). Thesubstrate 305 may comprise silicon, such as bulk silicon or silicon epion a bulk silicon substrate. The substrate 305 may also generallycomprise other materials, such as elementary semiconductors besidessilicon including germanium. Substrate 305 may also generally comprise acompound semiconductor.

Benefits of disclosed APD algorithms from using input voltage or currentvalues in a vectorized manner to determine the angular position of arotor for zero speed or near zero speed of a PMM for controlling PMMsinclude allowing the PMM to be started under motor control under a fullload. An arbitrary voltage (or current) input waveform can be used. Thesix vector input vector set method disclosed for 3-phase PMMs does notrotate the rotor of the PMM. A tuning procedure described in theExamples section below can be used to determine the voltage or currentvector magnitude and time duration for the input vectors. North-southrotor orientation is also determined automatically.

Disclosed algorithms can be implemented for angular positiondetermination for a variety of PMM controllers, for example for theTexas Instruments' INSTASPIN-FOC sensorless motor control technology,such as for PICCOLO and POTENZA MCU chip-based motor controllers. Theangular position determination can be used for position control,velocity control or current/torque control of the PMM. In the case ofINSTASPIN-FOC technology and related technology, code for the disclosedAPD algorithms can be embedded in the ROM of the MCU chip (see NV memory272 in FIG. 2B), such as to accelerate motor control development whileimproving efficiency. PMM control applications include for washingmachines, compressors, pumps, fans, electric bicycles, tools,treadmills, compact drives, sewing and textile machines, lifts and hobbymotors.

EXAMPLES

Disclosed embodiments are further illustrated by the following specificExamples, which should not be construed as limiting the scope or contentof this Disclosure in any way.

FIG. 4 is a flow chart that shows steps for an example method 400 ofdetermining the angular position of a rotor in an N-phase PMM using aninput vector set, according to an example embodiment. Step 401 comprisesproviding a processor having an associated memory storing an APD system,where the processor is programmed to implement the APD algorithm whichcauses an associated motor controller in a control loop with the PMMthrough connection to its respective stator phase winding terminals toexecute steps 402 to 405.

Step 402 comprises forcing one vector at a time a vector set of currentvectors or voltage vectors to the terminals of stator phase windings forthe N-phases of the PMM including a positive magnitude vector and anegative magnitude vector. The magnitude of the current vectors orvoltage vectors are all sufficiently small to not move (rotate) therotor. A time duration for the forcing of the respective current vectorsor voltage vectors is essentially fixed for a given motor.

Step 403 comprises measuring the resulting stator current or voltagelevels for each of the current or voltage vectors. The resulting statorcurrent or voltage levels are generally stored in a suitable memory.Step 404 comprises generating an N-dimension current vector or voltagevector from superposition of the resulting stator current or voltagelevels. For each of the N-dimensions of the resulting current or voltagevector, the largest absolute value of the current or voltage between thepositive and negative voltage or current vectors can be used.

Step 405 comprises using the N-dimension current vector or voltagevector to determine the angular position of the rotor. As noted above,in one embodiment the forcing comprises forcing voltage and sensingcomprises sensing resulting stator current. The sensing of the resultingstator current as known in the art can comprise using a circuitcomponent such as a resistor or a current sensor. In one particularembodiment the following position determination equation is employedwhich uses the N-resulting current levels in the N-dimension resultingcurrent vector to determine the angular position (θ) of the rotor for aN-phase PMM.

$\theta = {\tan^{- 1}\left( {- \frac{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\sin\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\cos\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}} \right)}$wherein N-phase measurements (i.e. x₁, . . . , x_(N)) (i.e., levels ofcurrent or voltage for phases 1, 2, . . . , N) are sensed from thestator current or stator voltage waveforms. Note, the above equationassumes that the respective phase responses have the same magnitude.

The above angular position determination equation or any other equationdescribed herein may be implemented by either hardware or by software.Regarding hardware-based implementations, a disclosed θ equation can beconverted to a logic gate pattern, such as using VHDL which can then berealized such as using field-programmable gate array (FPGA) orapplication-specific integrated circuit (ASIC) to implement the logicgate pattern. VHDL is an acronym which stands for VHSIC (Very High SpeedIntegrated Circuits) Hardware Description Language. For example, asoftware-based implementation can be realized using a math library on aMCU chip.

Experimental results were obtained from applying a disclosed initial APDsystem to a surface mounted PMM, the Estun Model #EMJ-04APB22 PMM, withthe results being calculated rotor angle response vs. rotor position asa function of rotor angle at 10 degree increments shown in FIG. 5 . TheDC bus voltage was 380V and the pulse time was 200 μs. It can be noticedthat there are a few nonlinear regions in the angle response due to thenonlinearities in the stator current waveforms. This phenomenon can beattributed to either the stator windings not being sinusoidal in shapeor to the stator core being driven into saturation when that statorphase is energized at the given rotor orientation. When driven intosaturation, the inductance of the stator changes, which introduces anonlinear warping into the current response because the current does notreach the level that it would have reached had the inductance notchanged. As a result, the stator current waveform can appear slightlywarped. However, the linearity of the rotor angle response is stillwithin tolerable limits for acceptable motor control of the PMM, whichhas an error of less than two degrees.

Those skilled in the art to which this disclosure relates willappreciate that many other embodiments and variations of embodiments arepossible within the scope of the claimed invention, and furtheradditions, deletions, substitutions and modifications may be made to thedescribed embodiments without departing from the scope of thisdisclosure.

The invention claimed is:
 1. A motor control system comprising: aprocessor wherein the processor receives digital values of N-phasemeasurements; wherein the processor is configured to generateN-dimension voltage vectors from superposition of selected ones of thedigital values of the N-phase measurements; a program memory wherein theprogram memory includes an angular position determination (APD)algorithm; wherein APD algorithm determines the angular position basedon the N-dimension voltage vectors; a pulse-width modulation (PWM)driver wherein the PWM driver generates a set of input vectors; and anAPD controller for controlling a signal generator; wherein the signalgenerator generates signals for the PWM driver.
 2. The motor controlsystem of claim 1, wherein the N-dimension voltage vectors arefundamental vectors.
 3. The motor control system of claim 1, wherein theangular position determination is determined by:$\theta = {\tan^{- 1}\left( {- \frac{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\sin\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\cos\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}} \right)}$wherein said x_(n) is stator voltage level.
 4. The motor control systemof claim 1, wherein the selected ones of the digital values of theN-phase measurements are identified for each of the N-phase measurementsby determining a largest absolute value of a difference between statorvoltage levels from a positive magnitude vector and a negative magnitudevector.
 5. The motor control system of claim 1, further comprising acontroller for controlling direct current.
 6. The motor control systemof claim 1, further comprising a controller for controlling quadraturecurrent.
 7. A motor control system comprising: a processor wherein theprocessor receives digital values of N-phase measurements; wherein theprocessor is configured to generate N-dimension current vectors fromsuperposition of selected ones of the digital values of the N-phasemeasurements; a program memory wherein the program memory includes anangular position determination (APD) algorithm; wherein APD algorithmdetermines the angular position based on the N-dimension currentvectors; a pulse-width modulation (PWM) driver wherein the PWM drivergenerates a set of input vectors; and an APD controller for controllinga signal generator; wherein the signal generator generates signals forthe PWM driver.
 8. The motor control system of claim 7, wherein theN-dimension current vectors are fundamental vectors.
 9. The motorcontrol system of claim 7, wherein the angular position determination isdetermined by:$\theta = {\tan^{- 1}\left( {- \frac{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\sin\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}{\sum\limits_{n = 1}^{N}{x_{n} \cdot {\cos\left( \frac{2{\pi \cdot \left( {n - 1} \right)}}{N} \right)}}}} \right)}$wherein said x_(n) is stator voltage level.
 10. The motor control systemof claim 7, wherein the selected ones of the digital values of theN-phase measurements are identified for each of the N-phase measurementsby determining a largest absolute value of a difference between statorcurrent levels from a positive magnitude vector and a negative magnitudevector.
 11. The motor control system of claim 7, further comprising acontroller for controlling direct current.
 12. The motor control systemof claim 7, further comprising a controller for controlling quadraturecurrent.